Out of all the many Undertale AUs out there, Zarla's Handplates is currently my favorite. It's deep, emotional and well-drawn, has great dialogue, and really makes the reader think about the different moral viewpoints the characters present. (Fair warning: If you're going to read it, prepare for pain, anger, and a potent urge to decapitate a fictional skeleton.)
It also has some goofy side comics, like the one where Gaster found a sexually explicit fanfiction Alphys had written, involving herself, him, and several other monsters.
This sparked a discussion about the logistics of Alphys dropping and possibly reattaching her tail, which resulted in me speculating about this interaction, which resulted in this picture.
Such a serious and poignant AU, and my first (but probably not last) fan art for it is a goofy one-panel about Alphys using a Finding Nemo reference while freaking out about Gaster (almost) touching her butt.
As a bonus for those of you who are familiar with this AU: Alphys is hiding in the same closet Gaster locked her in in this joke comic.
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